Hepatitis C (HCV) is the commonest cause of chronic hepatitis, cirrhosis and hepatocellular carcinoma (HCC) in the United States. HCC occurs primarily in patients with advanced fibrosis and cirrhosis from HCV. Current screening techniques involve the use of serum alfafetoprotein and liver imaging with ultrasound performed in high risk patients on a 3 to 6 monthly basis. Early detection can improve outcomes with liver transplantation and perhaps non-surgical therapies. However screening is not very effective and many patients present with large tumors or multifocal HCC with a median survival of only 6 months. There is a definite clinical need for better non-invasive biomarkers for HCC which can lead to early detection and treatment. The specific aims of this exploratory R21 proposal are to utilize a proteomic approach to identify novel biomarkers for HCC and then evaluate these biomarkers in a cohort of patients with HCV at high risk for HCC. The initial step will be identification of a matching group of patients with a high risk of HCC and those who have developed HCC during the prospective COPILOT study. The COPILOT study provides a large cohort of patients with HCV and cirrhosis who are randomized to treatment with either low dose PEGylated interferon alfa 2b or colchicine and are followed for 4 years with rigorous clinical screening for HCC. The study is in year 2 and the incidence of HCC is approximately 5%. Serum from these patients prior to and after the development of HCC is stored and will be utilized for proteomic studies. Tissue from normal liver and HCC is available from these patients who have undergone liver transplant. A control disease serum bank from patients with HCC unrelated to HCV is also available at BIDMC. The serum and tissue will be examined by proteomics for identification of novel biomarkers using SELDI-TOF mass spectrometry. Careful clinical characterization and matching will assist in the bioinformatic approach necessary to identify candidate biomarkers. Novel proteins and peptide biomarkers will be sequenced and identified and an ELISA will be developed for any promising candidate biomarkers. The candidate biomarker ELISA will then be validated in the large HCV serum bank at BIDMC of patients with all stages of HCV and those in the COPILOT trial. These studies may lead to identification of more specific and sensitive biomarkers for HCC in HCV which can then be validated further in prospective clinical trials.